NASA Moon Probe Sheds Light on Space Radiation Risks

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A NASA moon probe equippd with plastic that mimics living tissue
is helping researchers learn how deep-space radiation may affect
astronauts and electronics on future missions, researchers say.

These findings could lead to the development of leaner, more
efficient spacecraft that are better at balancing
radiation protection against weight, scientists added.

Potentially dangerous radiation pervades outer space, such as
electrically charged particles from the sun and high-mass,
high-energy cosmic rays known as HZE particles that emerge from
deep space. Earth's atmosphere and magnetic field block about
99.9 percent of this radiation, protecting those of us on the
planet's surface. [ Stunning
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"The atmosphere serves as just a big thick shield — the weight
exerted by the atmosphere is equivalent to a column of mercury
about 30 inches (76 centimeters) high, so you can think of the
atmosphere as a huge slab of dense metal a yard thick,"study lead
author Mark Looper, a space radiation physicist at The Aerospace
Corporation in El Segundo, Calif., told SPACE.com. "The magnetic
field, in addition, shunts aside most of the radiation from
Earth's surface."

To find out more about radiation hazards in space, Looper and his
colleagues are relying on the Cosmic Ray Telescope for the
Effects of Radiation instrument (CRaTER) aboard NASA's
Lunar Reconnaissance Orbiter, which has been zipping around
the moon at an altitude of about 30 miles (50 kilometers) since
2009.

CRaTER aims to measure not only radiation near
the moon, but also the effects radiation has on sensitive
materials such as human tissue or electronic parts that might
absorb it behind shielding. The instrument uses sensors behind
blocks of plastic designed to mimic the muscle tissue over a
person's radiation-sensitive bone marrow.

"We've never had such tissue-equivalent plastics as part of a
complex sensor in space before," Looper said.

The researchers found that although HZE particles only make up 1
percent or so of the radiation the telescope saw, "they made up
close to half of the energy deposited by radiation," Looper said.
"You get much more energy deposited by these heavies."

By looking with precision at the range of energies deposited by
various sources of radiation, scientists can estimate the effects
they might have. "It's like the difference between being hit with
a bat or a bullet — different kinds of radiation may deposit the
same amount of energy, but they distribute it differently,"
Looper said.

Altogether, these findings could help researchers optimize just
how much shielding spacecraft need without making them too heavy
for missions.

"The name of the game is risk management," Looper said. "To
decide how much shielding you need, you need to be able to
measure the effects. The more precision with which you can
measure those effects, the less likely you are to add more
shielding than you need, which is expensive and makes spacecraft
harder to launch."